Iron and zinc oxide nanoparticles: An efficient elicitor to enhance trigonelline alkaloid production in hairy roots of fenugreek

Fenugreek (Trigonella foenum-graecum L.) is a rich source of important medicinal metabolites. This plant belongs to the Fabaceae family that grows anywhere around the world. It is extensively used in medicine and as a food additive. Several secondary metabolites are detected in fenugreek, especially a valuable alkaloid called trigonelline. Enhancing the production of secondary metabolites is possible through the application of modern biotechnological techniques such as culturing hairy roots. In the present study, different strains of Agrobacterium rhizogenes (ATCC11325, ATCC15834, A4, A7, A13, and K599) were used for hairy root induction from fenugreek cotyledon explants. Then, the effect of various levels (x, 2x, and 4x concentrations of B5 medium) of iron oxide and zinc oxide nanoparticles were evaluated on growth, total phenolic, flavonoids, and trigonelline content of hairy roots. The growth curve analysis revealed an increase in the fresh and dry weight of treated hairy roots, as compared with the control. The highest levels of fresh (1.49 g) and dry weight (1.23 g) were obtained in hairy roots which were induced by the ATCC11325 strain and were treated with Zn (2x). The results indicated that using Zn nanoparticles on hairy roots can lead to higher levels of trigonelline, compared with the control group (i.e. transformed hairy roots without NPs).